Image display apparatus comprising a display device are known. Conventional examples of a display device include cathode ray tube type of image screen, more recent developments include LCD screens, plasma screens, etc. A major complaint with respect to especially large display apparatus is their non-aesthetic appearance when they are not in use. This hinders acceptance in consumers' homes. It is within the philosophy of some designers and interior architects to develop concepts where the display device is disguised by a static or dynamic architectural object. In other words unobtrusive design is considered to be relevant.
Ambient displays is the overall name for display apparatus that can display information in the on-state and are a decorative part of their environment in the off-state e.g. similar appearance as the wall in front of which the display apparatus is located. Typically, the display device of a display apparatus comprises light absorbing materials. The result is that the display apparatus looks like a “black hole” when it is turned off.
In order to prevent that “black hole” appearance it is proposed to provide the display apparatus with a disguising device arranged in front of the display device, i.e. at the viewing side of the display device. Such disguising device comprises a scattering layer, arranged to scatter a portion of the ambient light which falls on the scattering layer. With ambient light is meant, light that originates from any light source which does not belong to the display apparatus. The light source may be a lamp in the room in which the display apparatus is located. Ambient light may also be sun light coming through the windows of the room in which the display apparatus is located. With scattering is meant that light is directed in random directions. Scattering also comprises diffuse reflection. The effect of diffuse reflection is that a portion of the ambient light is directed in a forward direction, i.e. in the direction of a viewer of the display apparatus. Hence, the ambient light which falls on the display apparatus is no longer completely absorbed, because it is also partly reflected. Thus, as a result, the “black hole” appearance is substantially prevented.
The scattering layer may be arranged at some distance from the display device. However, it is preferred that the scattering layer is in close contact with the display device in order to obtain a thin display apparatus.
When investigating various types of materials it was found that currently commercially available scattering layers (PDLC, CTLC, polymer network LC based) do not offer sufficient hiding power to make the display device substantially invisible in its off state under the condition that the display device and the scattering layer are in relatively close contact. Depending on the type of effect and the thickness of the scattering layer the distance between the display device and scattering layer needed to be at least 4 cm.
Increasing the thickness of the scattering layer would improve the hiding power in some extend, and would result in a smaller distance between the display device and the scattering layer. However, the drawback of increasing the thickness of this scattering layer is an increase in the driving voltage. In addition the transmissive state will have a reduced transmission, and more residual haze.
It is an object of the invention to provide a display apparatus of the kind described in the opening paragraph with an improved hiding effect.